Plate trimmer control



0Ct 5, 1948 v A. o. BEHNKE ET AL PLATE TRIMMER CONTROL Filed. Dec. 5, 1945 Patented Oct. 5, 19.4.8

PLATE TRIMMER vCONTROL Albert 0. Behnke, Dayton, Ohio, and Charles Kregel, Wharton, Tex.

Application December 5, 1945, Serial No.- 633,033

(Cl. 315-3) f (Granted under the act of March '3, 1883, as amended April 3i), 1928; 370 -0. G. '757) 6 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a plate trimmer control for vacuum Atubes having plate structures which tend to resonate at certain of the frequencies at which the tubes are employed.

When vacuum tubes Yare used on the ultra high frequencies difficulty may be experience-d due to the fact that the plate structures tend to resonate at -some point or points vwithin the band. of frequencies in which the tube is operating. This Will be Aparticularly true if the plate 'structures have dimensions equal to one-quarter or one-half of the Wave length of the electrical oscillations. For example, if the tube is used as an oscillator and is provided with cooling fins for dissipating the heat generated in the plate it may be found that the tube will refuse to oscillate over a narrow band of frequencies in which the Wave length of the oscillations is such as to cause the cooling fins and the related plate structure to become electrically resonant and thereby absorb so much of the radio-frequency energy that the tube will cease -to function as an oscillator. We vhave found lthat this difficulty may be overcome by providing a suitable means `for selectively connecting-a trimming reactance to the plate structure and socausing the point of non-oscillation of the tube to be shifted either up or down the frequency scale. Thus, the entire band of frequencies for which the oscillator was designed may .be covered by connecting or disconnecting the trimming reactance from the plate as the oscillator is tuned through the band.

Accordingly, it is an object of our invention to provide a means for enabling a vacuum tube whose plate structure becomes electrically resonant at certain frequencies to operate throughout the entire band of frequencies for which it was designed.

`It 'isafurther object of our invention to provide means for selectively connecting a reactance to thel plate structure of a vacuum tube'for the purpose of shifting the frequencies at which nonoperation of the tube occurs due to the electrical Aresonance of the plate structurathereby enabling the tube to operate satisfactorily at these frequencies.

`It is still a Yfurther 'object of our invention to provide a manipulative means ifor selectively connecting a trimmer condenserto the platecooling fins of an air-cooled vacuum tube so as to shift the frequency at which the ns become selfresonant thereby enabling the tube Vto be operated over a continuous band of frequencies by proper manipulation of the manipulative means.

Still a further object of our invention resides in the provision of ya manipulative means vfor selectively connecting a trimmer capacitorto the plate cooling fins of an oscillator tube so as to shift the frequency at which the-hns become selfresonant thereby enabling the tube to oscillat'e over a continuous ban-d of frequencies.

Other objects and features of novelty will be apparent from the following description and the attached drawings, it being understood, however, that the invention is not limited to the specific embodiment disclosed lin the drawings or otherwise than by the appended claims.

Referring now to the drawings, in which-similar reference vnumerals refer to like parts:

Fig. 1 is an end View of a coaxial'line type of oscillator employing our invention, n

Fig. 2 is aside elevation of the oscillator tube and the plate trimmer control therefor,

Fig. 3 is a fragmentary cross-sectional view showing the plate cooling fins andthe mechanical structure for selectively connecting a trimmer capacitor with the fins, and,

Fig. 4 is a graph in which the power output of thevac-uum tube is plotted against the operating frequency, the solid line on the graph representing the operation of the tube with the trimmer capacitor disconnected from the cooling fins and the dotted line illustrating the operation of the tube with the trimmer capacitor connected to the cooling fins.

The present invention as shown inthe accompanying drawingsis applied to a transmitting tube of the lighthouse type having cooling fins attached to the plate of the tube for dissipating the heat generated in the plate by electronic bombardment. 'Thelig'hthouse transmitting tube is used in a coaxial line type of oscillating circuit, the tube being located inside of the concentric lines which form theoscillatcrcavity. The oscillator itself is designed for use in a transmitter of the type used for jamming enemyradio or radar stations. The transmitter is so constructed and arranged that it may be manually tuned through a comparatively wide band-of lfrequencies Yand thus used to jam any enemy radio or radar station .operating Within this band.

As shown in Figs. 1 and 2 of the drawings, `the lighthouse tube 2 is located within a cylindrical shield vor can 3 which is provided at its-open end with a mounting flange 4. The closed end of the shield 3 has been removed so as to expose the tube 2 and certain other parts of our invention located therein. The shield `."4 is secured to the outer sleeve f the cavity resonator (not shown) by means of a series of screws located around the flange 4. The lighthouse tube 2 is provided with a set of heat radiating fins S which are secured to a heat conducting rod 'l attached to the plate of the tube. The ns and tube are thus completely enclosed within the shield 3 and the outer sleeve of the cavity resonator. A pair of diametrically opposed holes 8 are provided in the cylindrical wall of the shield 3 for the purpose of enabling cooling air to be passed across the heat radiating ns B secured to the plate of the lighthouse tube.

As previously mentioned herein, the present invention resid-es in a means for selectively connecting a trimming reactance to the plate of the tube so as to shift the point of non-oscillation of the tube caused by the electrical resonance `of the fins 6 and the related plate structure at certain frequencies. This phenomenon is apparently due to the fact that 4a large part of the energy within the oscillatory circuit is dissipated among the plate fins and between .the fins and ground when the resonant frequency of the plate structure is reached. The frequency or frequencies at which this phenomenon occurs will be determined largely by .the .physical configuration and dimensions of the plate structure. Accordingly, when the cscillatory circuit is tuned over a givengjband of frequencies, there will be a sharp drop in the power output of the circuit when the resonant frequency of the cooling fins is reached,y which may result in a narrow frequency band of non-oscillation. f

In the present embodiment of the invention a small trimmer capacitor is utilized for the purpose of shifting the frequency at which resonance of the ns occurs although it is to be understood that a small reactance might also be used for shifting the point of non-oscillation of the tube to a higher or lower frequency.

As shown in Figs. 1, 2, and 3 the means for selectively connecting the reactance with .the plate `of the tube consists of a shaft 9 which is mounted for rotation in bearings I IJ and II secured to the framework of the transmitter. The shaft 9 is provided at one end with a slot I2 and at the other end with -a cam I4. The cam I4Vmay thus be rotated by means 4of a screwdriver inserted in the slot I2. The periphery of the cam I4 engages a cam follower I5 mounted on one end of a guide rod I1 which rod is journalled for longitudinal sliding movement within a brass bushing I8 screwed into lthe side wall of the tube shield 3. Ihe other end of the guide rod I1 is provided with screw .threads so as to enable it to be screwed into a tapped hole provided in an insulating block formed of Bakelite, polystyrene or ceramic material. A leaf spring contact 22 is secured to .the other end of the insulating block 20 by means of a screw 26 which is threaded into a tappe-d hole in the insulating block. A trimmer capacitor 28 of small capacity has one terminal connected to a .terminal lug clamped between the end of the block 2B and-the leaf spring contact 22 by means of the screw 2S and the other terminal connected to a terminal lug 21 which is forced over the end of the guide rod I'I. Inasmuch as the shield 3 is grounded as shown .in the drawings, it will be seen that the contact 22 is connected to ground through the trimmer capacitor 28. A compression spring 30 is adapted to slide over lthe bushing I8 and be compressed between the underneath side of the cam' follower IB and a threaded collar 32 which is screwed onto the base of the bushing I8. When the cam I4 is rota-ted by means of .the screwdriver adjustment I2 Ito bring the high side of the cam into contact with the cam follower I6, the block 2e, the condenser 28, and the contact 22 are moved to the left as viewed in Fig. 3 so as to Abring the contact into engagement with the cooling fins 6 which are secured to the plate of the lighthouse tube. This will place an additional capacitance across the resonant circuit formed bythe cooling ns 6 and .the related plate structure so as to vary the frequency at which the plate and n structure will resonate. The point of non-oscillation of the tube is thereby shifted so as to enable the tube to `oscillate through the frequencies which formerly constituted a dead spot in the band. If it is subsequently desired to tune .the transmitter to -a frequency within the new dead spot of the tube, the cam I4 may be rotated by means ,of the screwdriver adjustment I2 to bring .the low side of the cam into contact with the cam follower IE and allow the spring 30 to move the contact block and capacitor assembly -to the right as viewed in Fig. 3 to thereby disengage .the con-tact 22 `from the ns 6 and thus effectively remove the trimmer capacitor from the circuit.

The operation of the invention may be more clearly understood by referring to Fig. 4 which is a graph showing :the power output of the lighthouse tube plotted along the Y aXis and the frequency at which the 'tube is operated plotted along lthe X axis. The solid line on the graph represents the power output of the tube at various frequencies when 'the contact 22 is disengaged from the ns 6. The frequencies .through which the tube refuses to oscillate are shown on the graph to lie around 825 megacycles where the power output of the tube drops to Zero. The dotted line on the graph illustrates vthe operation of the tube when the contact 22 is brought into engagement with the fins yI5 so as to effectively place the trimmer capacitor between the plate of the tube and ground so as to alter the resonant frequency of .the plate structure. As noted on the graph, the point of non-oscillation of the -tube now lies in the region of 850 megacycles and it will be readily understood how :the tube can be made to oscillate throughout the entire band of frequencies by proper manipulation of the cam I4. Should more than one dead spot occur in the band to be covered, the same stratagem may be used for maneuvering the tube through these additional dead spots.

While the present invention has been shown and described in connection with a lighthouse tube having cooling ns attached to the plate for dissipating the heat generated by the electronic bombardment of the plate, it is evident that the invention could equally well be applied to any type of tube having a plate structure whose dimensions are such as to cause the same to resonate at some frequency within the operating band and thereby absorb such a large portion of the radio-frequency energy as to interfere with the proper operation ofy the tube and its related circuit.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. In combination with an air cooledv vacuum tube having plate cooling fins which tend to resonateat a frequency in the Iband of operating frequencies of the tube, a device for permitting normal operation of said tube throughout its operating band, said device comprising a grounded reactance means movably mounted adjacent said cooling fins to selectively connect said cooling ns to ground through said reactance means to shift the resonant frequency of said cooling fins thereby enabling said tube to operate through its entire frequency band.

2. The combination as set forth in claim 1 wherein said reactance means comprises capacitor means.

3. In combination with an air-cooled vacuum tube having plate cooling Vfins which tend to resonate at certain undesired frequencies, a contact member mounted adjacent said cooling fins, a reactance connected between said Contact member and a grounded point, and means for selectively engaging said contact member with said plate cooling ns to shift the frequency or frequencies at which said plate cooling fins become resonant thereby enabling said tube to operate through a continuous band of frequencies including the frequencies at which said fins become resonant.

4. Means for preventing undesired resonant effects in an oscillator tube provided with plate cooling fins which tend to resonate at certain frequencies, said frequencies comprising a contact member mounted adjacent said cooling fins, a condenser connected between said contact member and a grounded point, and manipulative means for selectively engaging said contact member with said plate cooling ns to shift the frequency or frequencies at which said plate cooling ns become resonant and thereby load the oscillator tube to cause it to cease oscillatingwhereby said oscillator tube may be caused to operate over a continuous band of frequencies including those frequencies at which said fins lbecome selfresonant.

5. In combination with a vacuum tube provided with a set of plate cooling fins which tend to resonate at certain undesired frequencies, a manipulable cam mounted adjacent said vacuum tube, a contact member movably mounted adjacent said ns to engage said fins upon manipulation of said cam, and a capacitor connected between said contact member and ground for shifting the frequency or frequencies at which said a manipulable cam mounted adjacent said oscillator tube, a grounded frame member, a cam follower slidably mounted in said frame member and in electrical Contact therewith, a spring for yieldably urging said cam follower into engagement with said cam, an insulating block secured to said cam follower, a leaf spring contact secured to said block and insulated from said cam follower, a trimmer capacitor having one of its terminals connected to said contact and the other of its terminals connected to said cam follower, said contact being adapted to -be moved into engagement with said cooling fins upon manipulation of said cam to shift the frequency or frequencies at which said cooling fins become resonant and load the oscillator tube to cause it to cease oscillating whereby said oscillator tube may be caused to operate over a continuous band of frequencies including those frequencies at which said ns become resonant.

ALBERT O. BEI-INKE. CHARLES KRIEGEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTSy Number Name Date 1,629,093 Curtis May 27, 1927 1,851,905 Hayes Mar. 29, 1932 2,143,658 Morris Jan. 10, 1939 2,181,817 Miller Nov. 28, 1939 2,193,500 Usselmann Mar. 12, 1940 FOREIGN PATENTS Number Country Date 340,615 Great Britain Jan. 5, 1931 Certificate of Correction Patent N o. 2,4=.'10,41J.V October 5, 1948.

ALBERT O. BEHNKE ET AL. f

It is hereby certifled that error appears in the printed specification of the above numbered patent requlrmg correction as follows:

Column 5, line 26, claim 4, for the Word frequencies second occurrence, read means;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oce.

Signed and sealed this 18th day of January, A.'D. 1949.

[IML] THOMAS F. MURPHY,

Assistant Uom/rnzssz'oner of Patents. 

